Camelina is recognized for its high oil content and richness in α-linolenic acid, a key precursor for omega-3 fatty acid biosynthesis; however, it is increasingly affected by drought stress associated with climate change. This study evaluated the effects of rosemary essential oil encapsulated in nanochitosan (NPs), applied individually or combined with arbuscular mycorrhizal fungi (AMF), on growth, physiological traits, antioxidant defense, and oil yield and composition of camelina under different irrigation regimes. A two-year field experiment was conducted using a split-plot design based on a randomized complete block with three replications. The main plots included full irrigation throughout the growing season (IR1), limited irrigation from flowering (IR2), and limited irrigation from pod formation (IR3). Subplots comprised no treatment, foliar application of NPs, AMF inoculation, and the combined use of NPs and AMF. Drought stress, particularly when initiated from flowering, markedly impaired photosynthetic pigments, nutrient assimilation, relative water content, seed yield, oil-related traits, and the extent of mycorrhizal colonization. In contrast, the combined application of NPs and AMF, compared to no treatment and individual applications, significantly improved seed and oil yield alongside enhanced chlorophyll fluorescence, nutrient availability, accumulation of antioxidant metabolites including phenolics, flavonoids, ascorbic acid, proline, soluble sugars, and tocopherols. It also increased mycorrhizal colonization, stimulated enzymatic antioxidant defenses, and reduced oxidative stress markers such as malondialdehyde and hydrogen peroxide. Additionally, the oil profile improved through an increased proportion of unsaturated fatty acids accompanied by a decrease in saturated fatty acids. Overall, the results suggest that the co-application of nanochitosan-encapsulated rosemary essential oil and AMF may offer a sustainable and potentially effective strategy to enhance drought tolerance and improve seed and oil quality in camelina under water-limited conditions.
